缩小图像尺寸

Question

我正在尝试减小用户从图库中选择的图像的大小，然后再将其传递给另一个意图。

我目前正在使用以下代码，但它似乎不起作用：

private Bitmap decodeFile(File f) throws IOException {
    Bitmap b = null;

    //Decode image size
    BitmapFactory.Options o = new BitmapFactory.Options();
    o.inJustDecodeBounds = true;

    FileInputStream fis = null;
    fis = new FileInputStream(f);

    BitmapFactory.decodeStream(fis, null, o);
    fis.close();

    int scale = 1;
    if (o.outHeight > IMAGE_MAX_SIZE || o.outWidth > IMAGE_MAX_SIZE) {
        scale = (int)Math.pow(2, (int) Math.ceil(Math.log(IMAGE_MAX_SIZE / 
           (double) Math.max(o.outHeight, o.outWidth)) / Math.log(0.5)));
    }

    //Decode with inSampleSize
    BitmapFactory.Options o2 = new BitmapFactory.Options();
    o2.inSampleSize = scale;
    fis = new FileInputStream(f);
    b = BitmapFactory.decodeStream(fis, null, o2);
    fis.close();

    return b;
}

Answer 1

最好的方法是通过意图传递图像路径，然后从那里降级图像。您不需要在当前活动上降级图像并传递降级的图像。

按照此处以降低您的图像read here。那里 使用 inSampleSize 会降低图像质量。 inSampleSize 越大，图像尺寸越小。

Answer 2

要压缩图像，您可以使用以下代码。

import android.graphics.Bitmap;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.media.ExifInterface;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class ImageResizer {

    public static String getCompressImageFile(File original, int width, int height, String filePath) {
        Bitmap sampledSrcBitmap = decodeFile(original, width, height);

        if(sampledSrcBitmap == null) {
            return null;
        }
        Bitmap bitmap = getRotatedImage(sampledSrcBitmap,original.getPath());

        int bitmap_width = bitmap.getWidth();
        int bitmap_height = bitmap.getHeight();

        boolean success;
        if(bitmap_width<width && bitmap_height <height){
            success = writeToFile(bitmap, new File(filePath),100);
        }else{
            bitmap = resize(bitmap, width, height);
            success = writeToFile(bitmap, new File(filePath),80);
        }
        bitmap.recycle();
        if(success){
            return filePath;
        }else{
            return null;
        }
    }

    private static Bitmap getRotatedImage(Bitmap sampledSrcBitmap,String path){
        ExifInterface exif;
        Matrix matrix = new Matrix();
        Bitmap bitmap=null;
        try {
            exif = new ExifInterface(path);
            int orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, 0);
            if (orientation == 6) {
                matrix.postRotate(90);
            } else if (orientation == 3) {
                matrix.postRotate(180);
            } else if (orientation == 8) {
                matrix.postRotate(270);
            }
            bitmap  = Bitmap.createBitmap(sampledSrcBitmap, 0, 0, sampledSrcBitmap.getWidth(), sampledSrcBitmap.getHeight(), matrix, true);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return bitmap;
    }

    public static Bitmap resize(Bitmap sampledSrcBitmap, int width, int height) {
        int sourceWidth = sampledSrcBitmap.getWidth();
        int sourceHeight = sampledSrcBitmap.getHeight();
        height = calculateHeight(sourceWidth, sourceHeight, width);
        return Bitmap.createScaledBitmap(sampledSrcBitmap, width, height, true);
    }

    private static int calculateWidth(int originalWidth, int originalHeight, int height) {
        return (int) Math.ceil(originalWidth / ((double) originalHeight/height));
    }

    private static int calculateHeight(int originalWidth, int originalHeight, int width) {
        return (int) Math.ceil(originalHeight / ((double) originalWidth/width));
    }

    public static Bitmap decodeFile(File bitmapFile, int reqWidth, int reqHeight){
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(bitmapFile.getAbsolutePath(), options);

        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
        options.inJustDecodeBounds = false;
        options.inDither = false;
        options.inPurgeable = true;
        options.inInputShareable = true;
        options.inPreferQualityOverSpeed = true;

        return BitmapFactory.decodeFile(bitmapFile.getAbsolutePath(), options);
    }

    public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
        if(reqWidth == -1) {
            reqWidth = options.outWidth;
        }

        if(reqHeight == -1) {
            reqHeight = options.outHeight;
        }

        // Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {
            if (width > height) {
                inSampleSize = Math.round((float) height / (float) reqHeight);
            } else {
                inSampleSize = Math.round((float) width / (float) reqWidth);
            }
        }

        return inSampleSize;
    }

    public static boolean writeToFile(Bitmap image, File file, int quality) {
        ByteArrayOutputStream bytes = new ByteArrayOutputStream();
        image.compress(CompressFormat.JPEG, quality, bytes);

        try {

            FileOutputStream fos = new FileOutputStream(file);
            fos.write(bytes.toByteArray());
            fos.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
            return false;
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }

        return true;
    }

}

并获取压缩图像路径调用 getComressImagePath 方法并提供选定的画廊图像路径进行压缩。将压缩图像路径传递给下一个活动，您可以使用它上传到服务器。

   public static String getComressImagePath(String picturePath){
         //Here 720 is max width and 1280 is max height. you can set this as per your need. Lower the resolution smaller the image size.
        return ImageResize.getCompressFile(new File(picturePath), 720, 1280, getTempImagePath());
   }

   public static String getTempImagePath(){
        File root = new File(Environment.getExternalStorageDirectory() + File.separator + "IMAGES");

        if (!root.exists()) {
            root.mkdirs();
        }

        File image = null;  
        image = new File(root+File.separator+"fileName");
        try {
           image.createNewFile();
           return image.getAbsolutePath();      
       } catch (IOException e) {
           e.printStackTrace();
       }

       return null;
   }

Answer 3

您可以使用此代码...

public static Bitmap getThumbnailBitmap(final String path,
        final int thumbnailSize) {
    Bitmap bitmap;
    BitmapFactory.Options bounds = new BitmapFactory.Options();
    bounds.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(path, bounds);
    if ((bounds.outWidth == -1) || (bounds.outHeight == -1)) {
        bitmap = null;
    }
    int originalSize = (bounds.outHeight > bounds.outWidth) ? bounds.outHeight
            : bounds.outWidth;
    BitmapFactory.Options opts = new BitmapFactory.Options();
    if (thumbnailSize > 0) {
        opts.inSampleSize = originalSize / thumbnailSize;
    } else {
        opts.inSampleSize = originalSize;
    }
    try {
        bitmap = BitmapFactory.decodeFile(path, opts);

    } catch (Exception ex) {
        return null;
    }
    return bitmap;
}